Square Tube Fabrication by Expansion Drawing of Circular Tube

An investigation was made on the application of expansion drawing for processing a circular parent tube to a square tube with high dimensional accuracy in this study. Influences of the dimensional parameters on thickness distribution and dimensional accuracy of the drawn tube were evaluated using finite element analysis. The parameters were plug width, plug half-angle, and plug corner shape. The material of the parent tube was aluminum alloy 1070. When the plug width was large, local thinning occurred on the corner of the drawn tube. When the plug width was small, a discrepancy in dimension occurred between the plug and the inner surface of the drawn tube. This discrepancy can be suppressed by using a plug with a small half angle. In addition, the local thinning was suppressed by using the plug which the cross-sectional shape was changed from a circle to a square in the taper portion. The results of experiments that followed the analyses were successfully in good agreement with the results of the analyses.